Permeability flow balancing within integral screen joints

ABSTRACT

A thermally assisted downhole system including a tubular configured to be disposed within an open hole borehole, the tubular being intended to be exposed to a heated fluid; a plurality of open hole anchors spaced along the tubular and engagable with the open hole, the anchors restricting longitudinal thermal growth of the tubular when engaged with the open hole.

BACKGROUND

Viscous hydrocarbon recovery is a segment of the overall hydrocarbonrecovery industry that is increasingly important from the standpoint ofglobal hydrocarbon reserves and associated product cost. In view hereof,there is increasing pressure to develop new technologies capable ofproducing viscous reserves economically and efficiently. Steam AssistedGravity Drainage (SAGD) is one technology that is being used andexplored with good results in some wellbore systems. Other wellboresystems however where there is a significant horizontal or nearhorizontal length of the wellbore system present profile challenges bothfor heat distribution and for production. In some cases, similar issuesarise even in vertical systems.

Both inflow and outflow profiles (e.g. production and stimulation) aredesired to be as uniform as possible relative to the particularborehole. This should enhance efficiency as well as avoid early waterbreakthrough. Breakthrough is clearly inefficient as hydrocarbonmaterial is likely to be left in situ rather than being produced.Profiles are important in all well types but it will be understood thatthe more viscous the target material the greater the difficulty inmaintaining a uniform profile.

Another issue in conjunction with SAGD systems is that the heat of steaminjected to facilitate hydrocarbon recovery is sufficient to damagedownhole components due to thermal expansion of the components. This canincrease expenses to operators and reduce recovery of target fluids.Since viscous hydrocarbon reserves are likely to become only moreimportant as other resources become depleted, configurations and methodsthat improve recovery of viscous hydrocarbons from earth formations willcontinue to be well received by the art.

SUMMARY

A thermally assisted downhole system including a tubular configured tobe disposed within an open hole borehole, the tubular being intended tobe exposed to a heated fluid; and a plurality of open hole anchorsspaced along the tubular and engagable with the open hole, the anchorsrestricting longitudinal thermal growth of the tubular when engaged withthe open hole.

A thermally assisted downhole system including a tubular within an openhole borehole, the tubular being exposed to a heated fluid; and aplurality of open hole anchors spaced along the tubular and engaged withthe open hole, the anchors restricting longitudinal thermal growth ofthe tubular.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings wherein like elements are numbered alikein the several figures:

FIG. 1 is a schematic view of a wellbore system in a viscous hydrocarbonreservoir;

FIG. 2 is a chart illustrating a change in fluid profile over a lengthof the borehole with and without permeability control.

DETAILED DESCRIPTION

Referring to FIG. 1, the reader will recognize a schematic illustrationof a portion of a SAGD wellbore system 10 configured with a pair ofboreholes 12 and 14. Generally, borehole 12 is the steam injectionborehole and borehole 14 is the hydrocarbon recovery borehole but thedisclosure should not be understood as limiting the possibilities tosuch. The discussion herein however will address the boreholes asillustrated. Steam injected in borehole 12 heats the surroundingformation 16 thereby reducing the viscosity of the stored hydrocarbonsand facilitating gravity drainage of those hydrocarbons. Horizontal orother highly deviated well structures like those depicted tend to havegreater fluid movement into and to of the formation at a heel 18 of theborehole than at a toe 20 of the borehole due simply to fluid dynamics.An issue associated with this property is that the toe 20 will sufferreduced steam application from that desired while heel 18 willexperience more steam application than that desired, for example. Thechange in the rate of fluid movement is relatively linear (decliningflow) when querying the system at intervals with increasing distancefrom the heel 18 toward the toe 20. The same is true for productionfluid movement whereby the heel 28 of the production borehole 14 willpass more of the target hydrocarbon fluid than the toe 30 of theproduction borehole 14. This is due primarily to permeability versuspressure drop along the length of the borehole 12 or 14. The system 10as illustrated alleviates this issue as well as others noted above.

According to the teaching herein, one or more of the boreholes(represented by just two boreholes 12 and 14 for simplicity inillustration) is configured with one or more permeability controldevices 32 that are each configured differently with respect topermeability or pressure drop in flow direction in or out of thetubular. The devices 32 nearest the heel 18 or 28 will have the leastpermeability while permeability will increase in each device 32sequentially toward the toe 20 and 30. The permeability of the device 32closest to toe 20 or 30 will be the greatest. This will tend to balanceoutflow of injected fluid and inflow of production fluid over the lengthof the borehole 12 and 14 because the natural pressure drop of thesystem is opposite that created by the configuration of permeabilitydevices as described. Permeability and/or pressure drop devices 32usable in this configuration include inflow control devices such asproduct family number H48688 commercially available from Baker OilTools, Houston Tex., beaded matrix flow control configurations such asthose disclosed in U.S. Ser. Nos. 61/052,919, 11/875,584 and 12/144,730,12/144,406 and 12/171,707 the disclosures of which are incorporatedherein by reference, or other similar devices. Adjustment of pressuredrop across individual permeability devices is possible in accordancewith the teaching hereof such that the desired permeability over thelength of the borehole 12 or 14 as described herein is achievable.Referring to FIG. 2, a chart of the flow of fluid over the length ofborehole 12 is shown without permeability control and with permeabilitycontrol. The representation is stark with regard to the profileimprovement with permeability control.

In order to determine the appropriate amount of permeability forparticular sections of the borehole 12 or 14, one needs to determine thepressure in the formation over the length of the horizontal borehole.Formation pressure can be determined/measured in a number of known ways.Pressure at the heel of the borehole and pressure at the toe should alsobe determined/measured. This can be determined in known ways. Once bothformation pressure and pressures at locations within the borehole havebeen ascertained, the change in pressure (ΔP) across the completion canbe determined for each location where pressure within the completion hasbeen or is tested. Mathematically this is expressed as ΔP location=Pformation−P location where the locations may be the heel, the toe or anyother point of interest.

A flow profile whether into or out of the completion is dictated by theΔP at each location and the pressure inside the completion is dictatedby the head of pressure associated with the column of fluid extending tothe surface. The longer the column, the higher the pressure. It follows,then, that greater resistance to inflow will occur at the toe of theborehole than at the heel of the completion. In accordance with theteaching hereof permeability control is distributed such that pressuredrop at a toe of the borehole is in the range of about 25% to less than1% whereas pressure drop at the heel of the borehole is about 30% ormore. In one embodiment the pressure drop at the heel is less than 45%and at the toe less than about 25%. Permeability control devicesdistributed between the heel and the toe will in some embodiments haveindividual pressure drop values between the percentage pressure drop atthe toe and the percentage pressure drop at the heel. Moreover, in someembodiments the distribution of pressure drops among the permeabilitydevices is linear while in other embodiments the distribution may followa curve or may be discontinuous to promote inflow of fluid from areas ofthe formation having larger volumes of desirable liberatable fluid andreduced inflow of fluid from areas of the formation having smallervolumes of desirable liberatable fluid.

Referring back to FIG. 1, a tubing string 40 and 50 are illustrated inboreholes 12 and 14 respectively. Open hole anchors 42, such as BakerOil Tools WBAnchor™ may be employed in the borehole to anchor the tubing40. This is helpful in that the tubing 40 experiences a significantchange in thermal load and hence a significant amount of thermalexpansion during well operations. Unchecked, the thermal expansion cancause damage to other downhole structures or to the tubing string 40itself thereby affecting efficiency and production of the well system.In order to overcome this problem, one or more open hole anchors 42 areused to ensure that the tubing string 40 is restrained from excessivemovement. Because the total length of mobile tubing string is reduced bythe interposition of open hole anchor(s) 42, excess extension cannotoccur. In one embodiment, three open hole anchors 42, as illustrated,are employed and are spaced by about 90 to 120 ft from one another butcould in some particular applications be positioned more closely andeven every 30 feet (at each pipe joint). The spacing interval is alsoapplicable to longer runs with each open hole anchor being spaced about90-120 ft from the next. Moreover, the exact spacing amount betweenanchors is not limited to that noted in this illustrated embodiment butrather can be any distance that will have the desired effect of reducingthermal expansion related wellbore damage. In addition the spacing canbe even or uneven as desired. The determination of distance betweenanchors must take into account. The anchor length, pattern, or thenumber of anchor points per foot in order to adjust the anchoring effectto optimize performance based on formation type and formation strengthtubular dimensions and material.

Finally in one embodiment, the tubing string 40, 50 or both isconfigured with one or more baffles 60. Baffles 60 are effective in bothdeterring loss of steam to formation cracks such as that illustrated inFIG. 1 as numeral 62 and in causing produced fluid to migrate throughthe intended permeability device 32. More specifically, and taking thefunctions one at a time, the injector borehole, such as 12, is providedwith one or more baffles 60. The baffles may be of any material havingthe ability to withstand the temperature at which the particular steamis injected into the formation. In one embodiment, a metal deformableseal such as one commercially known as a z-seal and available from BakerOil Tools, Houston Tex., may be employed. And while metal deformableseals are normally intended to create a high pressure high temperatureseal against a metal casing within which the seal is deployed, for thepurposes taught in this disclosure, it is not necessary for the metaldeformable seal to create an actual seal. That stated however, there isalso no prohibition to the creation of a seal but rather then focus isupon the ability of the configuration to direct steam flow withrelatively minimal leakage. In the event that an actual seal is createdwith the open hole formation, the intent to minimize leakage will ofcourse be met. In the event that a seal is not created but substantiallyall of the steam applied to a particular region of the wellbore isdelivered to that portion of the formation then the baffle will havedone its job and achieved this portion of the intent of this disclosure.With respect to production, the baffles are also of use in that thedrawdown of individual portions of the well can be balanced better withthe baffles so that fluids from a particular area are delivered to theborehole in that area and fluids from other areas do not migrate in theannulus to the same section of the borehole but rather will enter attheir respective locations. This ensures that profile control ismaintained and also that where breakthrough does occur, a particularsection of the borehole can be bridged and the rest will still producetarget fluid as opposed to breakthrough fluid since annular flow will beinhibited by the baffles. In one embodiment baffles are placed about 100ft or 3 liner joints apart but as noted with respect to the open holeanchors, this distance is not fixed but may be varied to fit theparticular needs of the well at issue. The distance between baffles maybe even or may be uneven and in some cases the baffles will bedistributed as dictated by formation condition such that for examplecracks in the formation will be taken into account so that a baffle willbe positioned on each side of the crack when considered along the lengthof the tubular.

While preferred embodiments have been shown and described, variousmodifications and substitutions may be made thereto without departingfrom the spirit and scope of the invention. Accordingly, it is to beunderstood that the present invention has been described by way ofillustration and not limitation.

1. A thermally assisted downhole system comprising: a tubular configuredto be disposed within an open hole borehole, the tubular being intendedto be exposed to a heated fluid; and a plurality of open hole anchorsspaced along the tubular and engagable with the open hole, the anchorsrestricting longitudinal thermal growth of the tubular when engaged withthe open hole.
 2. A thermally assisted downhole system as claimed inclaim 1 further including one or more baffles disposed along thelongitudinal extent of the tubular, the baffles being of sufficient sizeand thermal resistance to withstand and divert applied heated fluid. 3.A thermally assisted downhole system as claimed in claim 1 wherein theplurality of open hole anchors are spaced evenly.
 4. A thermallyassisted downhole system as claimed in claim 1 wherein the open holeanchors are spaced unevenly.
 5. A thermally assisted downhole system asclaimed in claim 1 wherein the space between each of the plurality ofopen hole anchors is selected to prevent movement of a liner relative tothe wellbore during temperature or pressure changes.
 6. A thermallyassisted downhole system as claimed in claim 1 further including one ormore baffles disposed along the longitudinal extent of the tubular, thebaffles being of sufficient size and thermal resistance to withstand anddivert applied heated fluid.
 7. A thermally assisted downhole system asclaimed in claim 1 wherein the one or more baffles are a plurality ofbaffles spaced evenly along the tubular.
 8. A thermally assisteddownhole system as claimed in claim 1 wherein the one or more bafflesare a plurality of baffles spaced unevenly along the tubular.
 9. Athermally assisted downhole system as claimed in claim 1 wherein the oneor more baffles are a plurality of baffles spaced as dictated byformation condition.
 10. A thermally assisted downhole systemcomprising: a tubular within an open hole borehole, the tubular beingexposed to a heated fluid; and a plurality of open hole anchors spacedalong the tubular and engaged with the open hole, the anchorsrestricting longitudinal thermal growth of the tubular.
 11. A thermallyassisted downhole system as claimed in claim 10 further including one ormore baffles disposed along the longitudinal extent of the tubular, thebaffles being of sufficient size and thermal resistance to withstand anddivert applied heated fluid.
 12. A thermally assisted downhole system asclaimed in claim 2 wherein the thermally assisted downhole system is aSAGD system.